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It could be just the thing for those who need a nudge to start ticking items off their bucket list; scientists have developed a blood test that reveals how long a person has left to live.
The test draws on nine biomarkers found in the blood that can be used to calculate the biological age of a person’s body – that is, how old it seems from the way it functions, as opposed to how long it has been out of the womb.
Researchers at Yale University in Connecticut found that the test was a more accurate predictor of life expectancy than a person’s chronological age or any of the biomarkers individually.
Morgan Levine, a pathologist at Yale, said the test could be used to identify people who are ageing faster than normal, meaning they are at greater risk than expected of disease and an early death.
“We showed that even among people who have no diseases, who are presumably healthy, we can still pick up differences in life expectancy. It’s capturing something preclinical, before any diseases present themselves,” she said.
“It’s picking up how old you look physiologically. Maybe you’re 65 years old but physiologically you look more like a 70 year old, so your mortality risk is more like that of a 70 year old.”
The test does more than reveal who is ageing well and who is not. With the results in hand, doctors can see what is contributing most to a person’s rate of ageing and suggest lifestyle changes that might reduce it.
“The biggest advantage of this is now being able to say someone’s at high risk, and that they should come in regularly so you can make sure they’re not developing this or that disease. It’ll show you how can you reduce their risk because you can plug all the numbers in and see how the risk drops if they bring their glucose down, for example,” Levine said.
To create the test, the scientists looked at 42 different clinical measures, such as white blood cell count, glucose and albumin levels, that were recorded for people who took part in two large studies as part of the US National Health and Nutrition Examination Surveys (NHANES). The studies gathered people’s medical and lifestyle details and were linked to death records.
The scientists used information from 10,000 people in the first study, which ran from 1988 to 1994, to identify clinical measures that most strongly predicted life expectancy. From this work, the scientists developed a combined test based on nine biomarkers which they validated in 11,000 people who had taken part in the second study, which ran from 1999 to 2010.
The test calculates what the scientists call a ‘phenotypic age’, which reflects the biological rather than chronological age of a person’s body. If a person’s phenotypic age is greater than their chronological age, they are ageing faster than average, and vice versa.
When the researchers ran the test on people who took part in the second NHANES study, they found that women typically had lower phenotypic ages than men, relative to their real ages, suggesting women age more slowly.
If a person’s biological age was much higher than their real age, their risk of dying younger shot up. Among 50- to 64-year-olds, a quarter of those ageing fastest died over the next ten years, compared with only a fifth of those ageing slowest among the 65- to 84-year-olds.
For each extra year that phenotypic age rose above chronological age, a person’s risk of dying in the study rose by 14% in the 20 to 39-year-old age group; 10% in the 40 to 64 year olds; and 8% in the 65- to 84-year-olds. Across the board, people who aged fastest had more diseases than those who aged more slowly.
“At younger ages most people aren’t going to die, you have to be a pretty extreme case. And it’s easier to figure out who those people are,” said Levine who posted details of the research on the online repository, Biorxiv. “But at the older ages, it becomes a little more random who is going to die, it’s almost about bad luck.”
In separate research, the team looked at what might drive accelerated ageing. The most important factors appeared to be growing up in a deprived neighbourhood, poor education and chronic stress, along with the usual lifestyle issues, such as smoking, doing too little exercise and obesity.
Levine believes that the new test is more useful than routine GP tests, such as blood pressure, which only highlight health problems when the results are above or below strict thresholds. “They miss the whole spectrum of risk,” she said. “We want to understand the risks for the majority of the population who are middle aged, who don’t have things wrong with them, and would be missed with traditional health assessments.”
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